This invention is related to growth stimulants for animals and, more particularly, to a complex glycoprotein growth stimulant derived from mammalian Zona pellucida for use in female ruminants such as heifers.
Innovations in farming and ranching have led to an industry that provides not only a livelihood for farmers and ranchers, but also, abundant quantities of food for the world's growing population and its increasing need for animal protein. Advances in food production have occurred as a result of technologic improvements in agriculture and animal science.
Raising domestic livestock, such as bovines (cattle), for red meat or beef production is an important part of producing food for the industrialized world's population. Usually, cattle intended for meat production are allowed to graze pastures until a desired weight is reached, and then additional weight is added in a feedlot prior to slaughter. Heifers fed in feedlots gain less weight than their male counterparts (steers or bulls), and this reduced weight gain increases the production cost for feeding heifers to acceptable weights for desired carcass quality.
Numerous practices are used in feedlot situations to decrease production costs for beef producers. Anabolic agents have been used for more than 20 years to promote and improve growth and to manipulate the metabolism of protein, carbohydrate, lipid and energy in cattle; see, for example, the article by Schanbacher, J. Animal Sci. 29:490 (1984). In commercial feedlots, heifers are implanted with and fed growth stimulants; see, for example, the articles by DeHaan et. al., J. Animal Sci. 68:2198 (1990), and Perry et. al., J. Animal Sci. 31:789 (1970). The implants are steroidal in nature and feed additives used with heifers include steroidal compounds (such as melengesterol acetate), ionophores, and antibiotics.
Antibiotics have been fed in beef cattle rations since the 1940's to improve growth and prevent disease; see, for example, the article by Utley et. al., J. Animal Sci. 34:339 (1972). Ionophores have been fed to cattle since 1977 to promote growth and improve the feed-to-gain conversion ratio. The feed-to-gain conversion ratio is a measurement of the efficiency of feed used to produce a gain in weight. A procedure that causes cattle to gain more weight on less feed has an improved feed-to-gain conversion ratio.
Melengesterol acetate is commonly used as a steroidal feed additive product for heifers and is fed daily in prepared rations; see, for example, the articles by Hill et. al., J. Animal Sci. 66:2435 (1988); Young, et. al., J. Animal Sci. 28:224 (1969); Hawkins et. al., J. Animal Sci. 35:1257 (1972); and Purchas et. al., J. Animal Sci. 33:836 (1971) and J. Animal Sci. 32:628 (1971). Melengesterol acetate is approved to be fed to beef heifers and its use leads to increased weight gain, improved feed efficiency and suppression of estrus (heat) in heifers.
The use of implants is the most effective method of decreasing the production cost of all the practices mentioned above. Implants are used more in the production of red meat in cattle than any other present management system; see, for example, the article by Faulkner et. al., J. Animal Sci. 67:1907 (1989) and Purchas et. al., J. Animal Sci. 32:628 (1971). Using diverse management systems including new and innovative methods, beef producers have been able to reduce production costs.
Presently, cattle may receive implants as many as 5 to 7 times from birth to slaughter; see, for example, the article by Simms, et. al., J. Animal Sci. 66:2736 (1989). Although this procedure results in improved feed-to-gain conversion, it requires frequent cattle handling.
There are other disadvantages to the use of implants and feed additives. Some foreign markets object to meat from heifers in which exogenous hormone supplementation has been used. For example, on Jan. 1, 1989, the European Economic Community (EEC) imposed a ban on American beef, claiming that growth hormones given to cattle could be a health hazard. The perceived fear of exogenous hormones, although not scientifically substantiated, has a psychological impact on the consumer. In addition, some feed additives may also be toxic if improperly mixed in feeds.
These and other limitations and disadvantages of the prior art are overcome by the present invention, and the use of Zona pellucida as an improved growth stimulant is provided.